This invention relates to tire assemblies and, more particularly, to a shield which is removably interposed between the tire rim and tire flap to prevent flap wear and tire blowouts.
Over the years, various improvements have been made to vehicle tires. These improvements have been directed primarily toward increasing the useful life of tires and reducing or eliminating operational tire failures such as blowouts, punctures, ply separations, and the like, thereby improving the safety of vehicular operation.
One area in which improvements have been directed is in the prevention of inner tube failure caused by the tube's interaction with the rim. For example, the invention disclosed in U.S. Pat. No. 1,658,646 sought to reduce inner tube failures through the use of an improved tire flap.
In recent years, there has been a reduction in the use of inner tubes for tires on light-duty vehicles, such as passenger cars. As a result, the largest present use of inner tubes in tires is in heavy-duty applications such as trucks, buses, and semi-trailers. Many of the recent developments in the art have been directed toward these applications. U.S. Pat. Nos. 3,533,461 and 4,063,584 both disclose tire flaps for heavy-duty vehicles which include improvements for reducing the wear on the inner tubes caused by the squeezing or pinching of the tubes between the flap and the tire of the wheel assembly. U.S. Pat. No. 2,773,535 discloses a metal plate which is incorporated and embedded in the tire flap during molding to reinforce the flap adjacent to the valve stem opening and to provide a rigid seat for the flanged end of the valve stem so as to prevent undesirable cocking and distortion of the valve stem.
Other devices have been added to fix the position of the valve stem, or to prevent the stem from being drawn into the tire when the inner tube deflates. Among these devices are those disclosed in U.S. Pat. Nos. 2,580,343; 2,968,206; 3,106,953; and 3,077,220.
Recent developments have significantly affected heavy-duty vehicular operations. These changes have at least indirectly helped create some of the problems which the present invention solves. Many states now permit trucks and other heavy-duty vehicles weighing up to 80,000 pounds gross to operate on the roads. Operators of these heavy-duty vehicles are also now inflating their tires to pressures in the range of 100-110 psi, since it has been shown that higher tire pressures conserve increasingly expensive fuel and extend the useful life of costly tires.
Increased loads, and increased tire pressures has resulted in tire failure from sources not often encountered with lighter loads, and lower pressures. In particular, the pressure now exerted by the inner tube against the tire flap tends to force portions of the tire flap through the valve stem opening in the wheel rim. This deformation eventually causes the tire flap to either wear thin or crack around the valve stem opening in the flap. The weakening of the tire flap results in stress being placed upon the inner tube, which, if the tire flap is not replaced, will ultimately result in failure and deflation of the inner tube. Besides the obvious safety hazards presented by a deflating tire during the operation of a heavy-duty vehicle, the tire itself may be destroyed. When a tube tire on a moving vehicle is suddenly deflated, an extremely large force is exerted upon the inner tube valve stem before the vehicle can be brought to a stop. Frequently, this force is great enough to draw the valve stem inwardly through the valve stem opening into the tire. Not only can this damage the valve stem, but the presence of the valve stem within the tire often damages the tire and the inner tube beyond repair before the vehicle can be brought to a halt.
Another way in which tire flaps can be damaged is through exposure to water, road salts, greases, oils, and road chemicals which weakens the rubber material of the flaps, and eventually causes them to deteriorate and break or crack. The flaps are protected in large part from these elements by the wheel rim. However, most wheel rims for heavy-duty vehicles have an elongated slot which is typically about 0.750 inch (1.905 cm) wide and 3.75 inches (9.525 cm) long for receiving the valve stem of the inner tube, leaving an unprotected area of the flap around the valve stem.
Standard industry practice is to reuse tire flaps a number of times. Because most of the tire flap is hidden from view, it is usually difficult to determine when the flap is wearing out, unless the tire is removed from the rim. Therefore, too often, tire flaps are not replaced before they have been damaged or become worn to the point where the inner tube ruptures and deflates.
Because of the number of flaps, inner tubes, and rims currently in use, it would be both impractical, wasteful, and extremely expensive to rectify the above-described problems by discarding viable present components and replacing them with improved components. It would be preferable to alleviate these problems with a device which is inexpensive, easy to install, and readily adapted to be used with equipment presently in service.